Gravity doesn't directly *pull* tectonic plates. Instead, it plays a crucial role in driving their movement through a process called slab pull. Here's how it works:

1. Subduction: When two tectonic plates collide, one denser plate (usually oceanic) slides beneath the other (continental). This process is called subduction.

2. Slab Pull: The subducted plate, now descending into the Earth's mantle, becomes denser and cooler. This colder, denser slab pulls the rest of the plate along with it, like a heavy anchor dragging a chain.

3. Gravity's Role: Gravity acts on this dense, descending slab, pulling it further into the mantle. This pull creates a force that helps drive the movement of the entire tectonic plate.

So, gravity doesn't pull the plate from above, but rather from within, as the descending slab is pulled down. This force, combined with other factors like ridge push (the force generated by the upwelling of magma at mid-ocean ridges), is responsible for the movement of tectonic plates across the Earth's surface.